Air classification of materials such as found in municipal waste, for example, is often performed in an inclined rotating drum wherein heavy materials deposited in the rotating drum are moved gradually and progressively downwardly and out the lower end of the drum while light materials become entrained in an air stream passing through the drum and are carried out the upper end of the drum. Such classifier apparatus is also used for many other applications such as in minerals and grain processing.
In such known apparatus, the light materials are carried by the air stream into a plenum chamber where they are in turn separated into light and heavy fractions, the heavy fractions dropping to the bottom of the chamber while the light fractions continue to be entrained within the air stream which passes upwardly and out the top of the plenum chamber into a cyclone collector.
The rotary drum which accomplishes the first separation is fed with mixed materials from a hopper or other supply source by a suitable conveyor, which may be a vibrator, belt or screen conveyor, which has its discharge end located adjacent to the inlet end of the drum. The air stream is created by a blower system located on the cyclone collector.
As an example of the prior art, reference may be made to abandoned U.S. application Ser. No. 580,373, assigned to the same assignee as the present invention.